Durable response to the ALK inhibitor alectinib in inflammatory myofibroblastic tumor of the head and neck with a novel SQSTM1–ALK fusion: a case report

An inflammatory myofibroblastic tumor (IMT) is a rare mesenchymal neoplasm that typically develops in the lungs and seldom in the head and neck region. It is often related to the anaplastic lymphoma kinase (ALK) fusion gene. Crizotinib, a first-generation ALK inhibitor, has been shown to have a notable response in patients with ALK-positive IMT. Here, we report the first case of a 46-year-old man with IMT harboring a novel SQSTM1–ALK fusion gene who demonstrated marked response to alectinib. The patient presented a right neck mass (5-cm diameter) that progressively enlarged and expanded to the upper mediastinum. ALK-rearranged IMT was diagnosed after complete tumor resection. Spindle cells displayed diffuse cytoplasmic staining for ALK on immunohistochemistry. A fluorescence in situ hybridization analysis revealed the translocation of a part of the ALK gene locus at chromosome 2p23. FoundationOne CDx™ assay identified an SQSTM1-ALK gene fusion. After a year, right cervical, subclavian, and mediastinal lymph node metastases, considered unresectable, developed. Notably, the patient exhibited a marked response to alectinib treatment and has sustained for 17 months following systemic therapy initiation without significant adverse events. This report highlights the possibility of alectinib being a reasonable option for advanced IMT with the SQSTM1-ALK fusion.